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• Yesterday, 11:45 AM
(ax+ b)(cx+ d)= acx^2+ (ad+ bc)x+ bd. So you want to find a, b, c, and d so that ac= 4, ad+ bc= 19, and bd= 12. 4 can be factored as 1*4 or as 2*2....
3 replies | 104 view(s)
• Yesterday, 10:38 AM
Using the fact, as suggested by tkhunny, that triangle STR is similar to triangle RTQ, we get \frac{9}{x}= \frac{x}{16}.
5 replies | 119 view(s)
• Yesterday, 10:33 AM
HallsofIvy replied to a thread sine,sos, tan in Geometry and Trig
To get the answers to what questions? I think any response would depend upon that! Of course tan(x) is defined as sin(x) divided by cos(x)...
3 replies | 119 view(s)
• 06-21-2018, 11:33 AM
HallsofIvy replied to a thread Interpolation in News
The Lagrange interpolation polynomial through the set of points (x_0, y_0), (x_1, y_1), ..., (x_{n-1}, y_{n-1}) is \sum_{i=0}^{n-1} y_i...
3 replies | 190 view(s)
• 06-19-2018, 10:06 AM
You were given that there were "4 giraffes, 3 lions, and 290 animals overall". You were asked "The number of giraffes is what percent greater...
5 replies | 366 view(s)
• 06-17-2018, 06:13 PM
Those are, in fact, the same answer. For n a positive integer, \Gamma(n)= (n-1)!. The way this is written is a little strange. Normally when you...
2 replies | 158 view(s)
• 06-02-2018, 07:22 PM
If you first divide 1600 by 3, you would get $533.33. If you add$100 to yours, that would be $633.33, If you subtract$50 from each of theirs, they...
8 replies | 370 view(s)
• 06-02-2018, 06:35 PM
your room mate is correct. If you each paid 1/3 of $1600 and one person paid an additional$100, then you would pay a total of 3(1600/3)+ 100=...
8 replies | 370 view(s)
• 06-02-2018, 07:48 AM
If yt is the dependent variable and x is the independent variable, then yt(a) and yt'(a) are simply numbers, not functions, and there is no way to...
3 replies | 476 view(s)
• 06-02-2018, 07:35 AM
Do you know what "domain" and "range" mean? What are possible values of this function? What is f(0)? What is f(1)?
6 replies | 345 view(s)
• 06-02-2018, 07:33 AM
There simply isn't enough information to tell us what is in the "..." section. The first two terms might imply "nx\Delta x but the last term...
3 replies | 183 view(s)
• 06-02-2018, 07:28 AM
Do you know the basic definitions of |x| and \sqrt{x}? |x| is defined as: x if x\ge 0, -x if x< 0. So |x| is never negative. \sqrt{x} is defined...
8 replies | 350 view(s)
• 06-01-2018, 07:26 AM
Yes, looks like a typo to me. In the solution they are clearly taking both A and B to be in the third quadrant.
1 replies | 144 view(s)
• 05-31-2018, 11:16 AM
The vertical line is x= 4. Any line through (0, 0) has equation y= ax. Since it goes through (4, 11) 11= 4a so a= 11/4. The equation of that line...
2 replies | 135 view(s)
• 05-31-2018, 07:53 AM
What do you mean by "square top b square bottom a"? That the top is a square with side length b and the bottom is a square with side length a? If...
17 replies | 596 view(s)
• 05-30-2018, 07:51 AM
Part (a) of this problem says "create a scatter plot". Have you done that? Do you know what a "scatter plot" is? Once you have done that, the...
8 replies | 463 view(s)
• 05-30-2018, 07:47 AM
The crucial thing is that the equation be linear so that you can add different solutions to get a new solution.
14 replies | 832 view(s)
• 05-28-2018, 06:51 AM
"Integration by parts" is the reverse of "the product rule" for differentiation. \frac{d(uv)}{dx}= u\frac{dv}{dx}+ v\frac{du}{dx}. ...
6 replies | 259 view(s)
• 05-27-2018, 07:05 PM
I feel compelled to respond to "A differential equation like y'' + y = o is important because it appears in physics." Well, if you are a physicist...
14 replies | 832 view(s)
• 05-27-2018, 06:45 PM
So you are actually using cylindrical coordinates with z= e^{-r^2} for all \theta. The "differential of area" in polar coordinates is r drd\theta so...
2 replies | 163 view(s)
• 05-26-2018, 03:09 PM
I presume, since you are asking about differential equations, that you have taken calculus and know that y'' is the second derivative. If, for...
14 replies | 832 view(s)
• 05-26-2018, 12:05 PM
Yes, it is the rate, in feet per second, at which the length of the shadow is increasing.
8 replies | 354 view(s)
• 05-26-2018, 10:26 AM
If v is a vector depending on t, then dv/dt is also a vector. In particular, if v is a three dimensional vector then dv/dt is a three dimensional...
5 replies | 332 view(s)
• 05-26-2018, 10:24 AM
If v is a vector depending on t, then dv/dt is also a vector. In particular, if v is a three dimensional vector then dv/dt is a three dimensional...
5 replies | 332 view(s)
• 05-26-2018, 08:50 AM
No, it isn't. You said earlier "and "z" is the hypotenuse of the triangle (distance from the street light to the tip of the man's shadow)". Since...
8 replies | 354 view(s)
• 05-26-2018, 08:44 AM
Yes, the difference quotient for \sqrt{x} is \frac{\sqrt{x+ h}- \sqrt{x}}{h}. I presume you know that (a- b)(a+ b)= a^2- b^2. To get rid of the...
3 replies | 167 view(s)
• 05-26-2018, 08:32 AM
??? There is nothing at all in the definition of the vector that says it is a function of t! (I know the "null space" of a linear operator but...
5 replies | 332 view(s)
• 05-26-2018, 08:26 AM
The first problem is: Two species of Macaw inhabit a patch of trees. 85% of the birds are blue tailed and 15% are red tailed. They feed at dawn. A...
2 replies | 162 view(s)
• 05-25-2018, 03:48 PM
What is the "·" between "(∇ × F)" and "(∇ · F)" supposed to mean? You have used it elsewhere as the dot product and wrote scalar multiplication as...
2 replies | 179 view(s)
• 05-25-2018, 01:39 PM
So 5/6(42)= 35 workers in the concession stand are wearing name tags. 88- 35= 53 workers, not in the concession stand, are also wearing name tags. ...
4 replies | 316 view(s)
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